Effects of current on the microstructure and frictional behavior of Ni/CNTs films fabricated on Cu substrates

Purpose Due to their excellent wear resistance and superior thermal conductivity, copper (Cu) is an ideal choice for transmission parts. However, under continuous high-frequency cyclic loading, the coefficient of friction (COF) of Cu may fluctuate, leading to decreased lubrication performance and increased wear. This degradation causes bearing service life to decline, thereby compromising the integrity and stability of the mechanical system. The purpose of this study is to overcome these challenges, and surface modification via film-deposition technology has been developed. This technology involved forming a surface film with specific properties on Cu substrates to enhance their surface properties, particularly wear resistance, corrosion resistance and lubrication performance, thereby extending the service life of bearings. Design/methodology/approach In this study, a Nickel/Carbon Nanotubes (Ni/CNTs) composite film via composite electrodeposition was fabricated. This technique offers advantages of simple operation and short deposition time. The influence of different current during electrodeposition processes on the films were investigated. In addition, tribological properties of Ni/CNTs films sliding against GCr15 steel were evaluated under dry friction at sliding speeds varied from 0.042 to 0.2 m/s. Findings The thickness of the Ni/CNTs films was approximately 48 µm. The adhesion strength of the Ni/CNTs film was determined to be approximately 24 N. As the current increased, the surface nodules of the film increased and the surface roughness gradually increased. As the current increased, the hardness of the film initially increased, followed by a decrease, but all were much higher than the hardness of Cu. Under the optimal current of 0.8A, the hardness of film was improved by 176.3% in comparison to the substrate. The corrosion resistance of the film first increased and then decreased with increasing current. At the current of 0.8A, the film exhibited the optimal corrosion resistance. With the increased of electrodeposition current in the bath, the microstructure of Ni/CNTs film became porous. At various sliding speeds, the film prepared under 0.8A current exhibited the best wear reduction and wear resistance, especially at a speed of 0.048 m/s, where the COF of this film was decreased by 17.89% in comparison to the substrate. Originality/value To mitigate this, organic surfactants are commonly used to stabilize CNTs suspensions. Despite extensive studies on the CNTs films, far less is known about their specific role in the tribological behavior of Ni/CNTs films.